Process control system with improved fault isolation
First Claim
1. In a control system for providing direct digital control over an industrial process of the type having a digital controller communicating with a plurality of sensors and actuators located within a process field area, said controller including in a first location a central processing unit and associated data storage means for performing operations respecting the condition of said process and in a second location an input/output connector housing area for holding a plurality of input/output modules that receive and send field signals to and from said sensors and actuators, said controller further including a communications bus linking said first and second locations such that said input/output modules are connected in parallel along said bus when inserted in said connector housing area, the improvement in said control system for detecting and isolating failures within said controller comprising:
- means for detecting a fault condition within said controller;
means responsive to said detector means for providing an indication of said fault condition;
means for isolating said fault condition between either said first location or said second location;
said means for isolating including means for rapidly disconnecting said input/output modules from said first location, whereby the absence or continuance of said fault indication pinpoints whether said fault condition is in said first or second location.
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Accused Products
Abstract
A process control system includes redundant digital controllers and a plurality of input/output (I/O) modules for interfacing with remote field sensors and actuators. Bi-directional communication between controllers and I/O modules is achieved by a parallel-wired, process I/O bus. Failures within the system, including the bus structure itself, that continually keep the bus active (i.e., in a low state) are isolated by a combination of software diagnostic routines for performing bus checkout and a unique quick disconnect feature that readily isolates the fault condition first between the I/O module nest area and the controllers, then, if necessary, to individual I/O modules. During fault isolation procedures, individual I/O modules may be disconnected from the bus while the values of field signals are simultaneously maintained to provide minimum process upset.
129 Citations
24 Claims
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1. In a control system for providing direct digital control over an industrial process of the type having a digital controller communicating with a plurality of sensors and actuators located within a process field area, said controller including in a first location a central processing unit and associated data storage means for performing operations respecting the condition of said process and in a second location an input/output connector housing area for holding a plurality of input/output modules that receive and send field signals to and from said sensors and actuators, said controller further including a communications bus linking said first and second locations such that said input/output modules are connected in parallel along said bus when inserted in said connector housing area, the improvement in said control system for detecting and isolating failures within said controller comprising:
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means for detecting a fault condition within said controller; means responsive to said detector means for providing an indication of said fault condition; means for isolating said fault condition between either said first location or said second location; said means for isolating including means for rapidly disconnecting said input/output modules from said first location, whereby the absence or continuance of said fault indication pinpoints whether said fault condition is in said first or second location. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In a control system for providing direct digital control over an industrial process of the type having a digital controller communicating with a plurality of sensors and actuators located within a process field area, said controller including in a first location a central processing unit and associated data storage means for performing operations respecting the condition of said process and in a second location an input/output connector housing area for holding a plurality of input/output modules that receive and send field signals to and from said sensors and actuators, said control system further including a communications bus linking said first and second locations such that said input/output modules are connected along said data bus when inserted in said connector housing area, said modules being powered from said bus connection and a separate field connection for providing field power to said sensors and actuators, the improvement in said control system comprising:
means for disengaging said input/output modules from said bus while simultaneously maintaining said field connection. - View Dependent Claims (12, 13, 14, 15, 16)
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17. In a control system for providing direct digital control over an industrial process of the type having a digital controller communicating with a plurality of sensors and actuators located within a process field area, said controller including in a first location a central processing unit and associated data storage means for performing operations respecting the condition of said process and in a second location an input/output connector housing area for holding a plurality of input/output modules that receive and send field signals to and from said sensors and actuators, said controller further including a communications bus and associated cable means electrically linking said first and second locations such that said input/output modules are connected to said bus when inserted in said connector housing area, said controller also receiving at said modules field signal cables for communicating with said process field area, the improvement in said control system for detecting and isolating failures within said controller comprising:
means for disconnecting said input/output modules from said bus in situ within said connector housing area without altering the position of either said cable means or said field signal cables. - View Dependent Claims (18, 19)
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20. An improved method for detecting and isolating failures within a direct digital control system of the type having a digital controller communicating with a plurality of sensors and actuators located within a process field area, said controller including in a first location a central processing unit and associated data storage means for performing operations respecting the condition of said process and in a second location an input/output connector housing area for holding a plurality of input/output modules that receive and send field signals to and from said sensors and actuators, said controller further including a communications bus linking said first and second locations such that said input/output modules are connected in parallel along said bus when inserted in said connector housing area, comprising the steps of:
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detecting a fault condition within said controller; providing an indication of said fault condition; isolating said fault condition between either said first location or said second location by rapidly disconnecting said input/output modules from said first location. - View Dependent Claims (21, 22, 23, 24)
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Specification